Fixed #16281 -- Fixed ContentType.get_object_for_this_type() in a multiple database setup.

tests/admin_views/models.py

@@ -83,6 +83,9 @@ class Book(models.Model):
     def __str__(self):
         return self.name
 
+    def get_absolute_url(self):
+        return f"/books/{self.id}/"
+
 
 class Promo(models.Model):
     name = models.CharField(max_length=100, verbose_name="¿Name?")

tests/admin_views/test_multidb.py

@@ -2,6 +2,8 @@ from unittest import mock
 
 from django.contrib import admin
 from django.contrib.auth.models import User
+from django.contrib.contenttypes.models import ContentType
+from django.http import HttpResponse
 from django.test import TestCase, override_settings
 from django.urls import path, reverse
 
@@ -23,8 +25,15 @@ class Router:
 site = admin.AdminSite(name="test_adminsite")
 site.register(Book)
 
+
+def book(request, book_id):
+    b = Book.objects.get(id=book_id)
+    return HttpResponse(b.title)
+
+
 urlpatterns = [
     path("admin/", site.urls),
+    path("books/<book_id>/", book),
 ]
 
 
@@ -88,3 +97,47 @@ class MultiDatabaseTests(TestCase):
                     {"post": "yes"},
                 )
                 mock.atomic.assert_called_with(using=db)
+
+
+class ViewOnSiteRouter:
+    def db_for_read(self, model, instance=None, **hints):
+        if model._meta.app_label in {"auth", "sessions", "contenttypes"}:
+            return "default"
+        return "other"
+
+    def db_for_write(self, model, **hints):
+        if model._meta.app_label in {"auth", "sessions", "contenttypes"}:
+            return "default"
+        return "other"
+
+    def allow_relation(self, obj1, obj2, **hints):
+        return obj1._state.db in {"default", "other"} and obj2._state.db in {
+            "default",
+            "other",
+        }
+
+    def allow_migrate(self, db, app_label, **hints):
+        return True
+
+
+@override_settings(ROOT_URLCONF=__name__, DATABASE_ROUTERS=[ViewOnSiteRouter()])
+class ViewOnSiteTests(TestCase):
+    databases = {"default", "other"}
+
+    def test_contenttype_in_separate_db(self):
+        ContentType.objects.using("other").all().delete()
+        book = Book.objects.using("other").create(name="other book")
+        user = User.objects.create_superuser(
+            username="super", password="secret", email="super@example.com"
+        )
+
+        book_type = ContentType.objects.get(app_label="admin_views", model="book")
+
+        self.client.force_login(user)
+
+        shortcut_url = reverse("admin:view_on_site", args=(book_type.pk, book.id))
+        response = self.client.get(shortcut_url, follow=False)
+        self.assertEqual(response.status_code, 302)
+        self.assertRegex(
+            response.url, f"http://(testserver|example.com)/books/{book.id}/"
+        )